2 replies to this topic

[Mithun_mk]

Dear all,

 

I am designing a atmospheric storage tank for a chemical which is 2.8m diameter and 13m height. L/D ratio is 4.5. Is this a problem. I have installed a tank with 4m diameter and 12m height in the past which is working fine. Is there any upper limit for the L/D ratio for atmospheric tanks?

 

Mithun

[Art Montemayor]

 

Mithun

 

If you are “designing” the atmospheric tank, then you are responsible for all the mechanical specifications for it – such as wind, seismic, live loads, and other forces acting on the tank.  In addition, if you have a 13 meter high tank, you will surely require structural items attached to it for platforms, ladders, lighting, etc.  all this means that you must ensure the mechanical stability of the tank while it is in operation – and not only calculate the wall thickness due to internal pressure.  You may also have to design for external pressure (partial vacuum), especially if you intend to apply an inert gas blanket now or in the future.

 

The only person who can determine if you have a “problem” is yourself (or your designers and fabricators).  We on the Forum certainly can’t – at least not with the lack of data that you furnish.

 

[chemsac2]

Mithun,

 

Logic behind certain L/D values is economics. E.g. vessels overall cost is found minimum when L/D is between 3-4. But that does not mean, other L/D ratios would not be feasible.

 

For tanks, L/D of around 1 is recommended to avoid expensive civil foundation. Tank height is set by soil bearing capacity. Too high a tank would call for either ring-beam or pile foundation which would be costly for big storage tanks.

 

As long as your Civil designer takes care of foundation design and that is economical for you, this L/D should not be a problem.

 

Regards,

 

Sachin